Light stabilizer composition

ABSTRACT

The invention relates to a light stabilizer composition obtainable by the process comprising the steps of 
     a) mixing a polymer with at least one polyalkylpiperidine and at least one free radical generator 
     b) melt-blending of that mixture at a temperature above the melting point of the polymer and above the decomposition temperature of the free radical generator and at shear conditions sufficient to blend the components. 
     The invention also provides a method for enhancing the light stability of polymers, preferably polyolefins.

The invention relates to stabilizer compositions as well as to a methodfor enhancing the light stability of polymers, in particularpolyolefins.

It is the object of the present invention to provide an improvedstabilizer composition for stabilizing polymers, in particularpolyolefins, against the damage effected by light.

This object is achieved with the stabilizer composition as hereinunderdescribed. It has surprisingly been found that masterbatch compositionsof polyalkylpiperidines prepared in the presence of a free radicalgenerator, exhibit an increased stabilization activity compared to thestabilization activity of masterbatch compositions according to theprior art which are produced without the addition of a free radicalgenerator.

Accordingly, the present invention provides a light stabilizercomposition obtainable by the process comprising the steps of

a) mixing a polymer with at least one polyalkylpiperidine and at leastone free radical generator

b) melt-blending of that mixture at a temperature above the meltingpoint of the polymer and above the decomposition temperature of the freeradical generator and at shear conditions sufficient to blend thecomponents.

The melt-blending temperature varies with the type of polymer and thetype of the free radical generator. The skilled person can readilyascertain the appropriate temperature but a typical temperature rangecomprises the range from about 130° C. to about 300° C., preferably therange from about 150° C. to about 230° C.

The free radical generator is preferably a peroxide or hydroperoxidecompound, in particular an organic peroxide compound. Suitable freeradical generators are selected from the group consisting of dicumylperoxide; 2,5-bis-tert.-butylperoxy-2,5-dimethylhexane;di-tert.-butyl-peroxide; isopropyl-tert.-butyl peroxy carbonate;bis-(tert.-butyl-2-peroxyisopropyl)-1,3-benzene;dimethyl-2,5-bis-(tert.-butylperoxy)-2,5-hexane;dimethyl-2,5-bis-(tert.-butylperoxy)-2,5-hexine-3; tert.-(butylcumylperoxide, bis-(tert.-butyl)-3,3-ethyl butyrate.

The polyalkylpiperidine is an oligomeric or a high molecular-weightpolyalkylpiperidine or a low molecular-weight polyalkylpiperidine or apolymer bound polyalkylpiperidine.

Preferably, the oligomeric or high molecular-weight polyalkylpiperidineis selected from the group consisting of compounds of formulae (I) to(VIII):

poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetra-methyl-piperidyl)-amino]-hexamethylene-[4-(2,2,6,6-tetramethylpiperidyl)-imino]}(I)

[Commercially available for example as Chimassorb (registered trademark)944 (Ciba Specialty Chemicals Inc.)]

1,3,5-triazine-2,4,6-triamine,N,N′″-1,2-ethanediylbis[N-[3-[[4,6-bis[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazin-2-yl]methylamino]propyl]-N′,N″-dibutyl-N′,N″-bis-(1,2,2,6,6-pentamethyl-4-piperidinyl)-(II)

[Commercially available for example as Chimassorb (registered trademark)119 ((Ciba Specialty Chemicals Inc.)]

poly[(6-morpholino-s-triazine-2,4-diyl)[2,2,6,6-tetramethyl-4-piperidyl)-imino]-hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino](III)

[Commercially available for example as Cyasorb (registered trademark) UV3346 (American Cyanamid Inc.)]

poly-(N-β-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidyl-succinate)(VI)

[commercially available for example as Tinuvin (registered trademark)622 (Ciba Specialty Chemicals Inc.).

polymethylpropyl-3-oxy-[4(2,2,6,6 tetramethyl)-piperidinyl]-siloxane (V)

[Commercially available for example as Uvasil (registered trademark) 299(Great Lakes Chemical Corp.)]

Oligomer obtained by the reaction and subsequent oligomerization of2,2,4,4-tetramethyl-21-oxo-7-oxa-3,20-diazadispiro-[5.1.11.2]-heneico(VI) sane or its hydrochloride with epichlorohydrine.

[Commercially available for example as Hostavin (registered trademark)N-30 (Hoechst)]

1,3-propanediamine, N,N″-1,2′-ethanediyl-bis-, polymer withN-butyl-2,2,6,6-tetramethyl-4-piperidinamine and2,4,6-trichloro-1,3,5-triazine (VII)

[commercially available for example as Uvasorb (registered trademark)HA-88]

poly-[3-eicosyl(-tetracosyl)-1-(2,2,6,6-tetramethylpiperidine-4-yl)-pyrrolidine-2,5-dione](VIII)

[commercially available for example as Uvinul 5050 H]

Preferably, the low molecular-weight polyalkylpiperidine is selectedfrom the group consisting of compounds of formulae (IX) to (XIII)

bis-2,2,6,6-tetramethyl-4-piperidyl-sebacate (IX)

[commercially available for example as Tinuvin (registered trademark)770 (Ciba Specialty Chemicals Inc.)]

propanedioic acid,[(4-methoxyphenyl)-methylene]-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-ester](X)

[Commercially available for example as Sanduvor (registered trademark)PR 31 (Clariant)]

a mixture of esters of 2,2,6,6-tetramethyl-4-piperidinol and higherfatty acids (mainly stearic acid) (XI)

[commercially available for example as Dastib (registered trademark) 845or Cyasorb (registered trademark) UV 3853]

2,2,6,6-tetramethyl-21-oxo-7-oxa-3,20-diazadispiro[5.1.11.2]-heneicosane(XII)

[commercially available for example as Hostavin (registered trademark)N-20 (Hoechst)]

2,2,4,4-tetramethyl-21-oxo-7-oxa-3,20-diazadispiro[5.1.11.2]-heneicosan-20-propanoic-acid-dodecyles(XIII)

[commercially available for example as Hostavin (registered trademark)N-24 (Hoechst)].

The polyalkylpiperidine is typically used in an amount of from 0.1 to70% by weight, preferably from 5 to 30% by weight based on the weight ofthe polymeric composition.

Typical quantities of the free radical generator is from 0.01 to 10% byweight, preferably from 0.1 to 2% by weight based on the weight of thepolymeric composition.

All compounds of formulae (I) to (XIII) are known or may be made fromknown compounds by known methods.

The polymer of the stabilizer composition according to the invention isa thermoplastic organic polymer, preferably selected from polyolefinsand copolymers and blends thereof.

Further additives, which may be added, if appropriate, includeantioxidants, UV-absorbers, pigments, dyes, nucleating agents, fillers,and property modifiers and several others commonly used.

A further object of the invention is a method for enhancing the lightstability, preferably UV light stability, of polymeric materials,preferably thermoplastic organic polymers, which are identical orcompatible with the polymer component of the stabilizer compositionaccording to the invention. This method comprises incorporating beforeor during processing a stabilizing quantity of the stabilizingcomposition according to the invention into the polymeric material to bestabilized. The quantity of the light stabilizer composition accordingto the invention needed to confer an appreciable extent of stabilizationvaries with the amount of the polyalkylpiperidine compound as well aswith the type of the polymer and the end use of the finished article.The skilled person can readily ascertain the appropriate quantity forthe diverse fields of applications.

LIST OF THE SUITABLE FREE RADICAL GENERATORS

The invention is further illustrated by means of the following examplesin which all parts are expressed by weight.

EXAMPLE 1

15%-compositions of polyalkylpiperidines in polypropylene (MFI=0.7 g/10min at 230° C. and 2.16 kg) were prepared with different amounts of thefree radical generator (FRI) 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexane,as shown in Table 1. The compositions were first dry blended and thenmelt processed in a Brabender kneader at 200° C. during 10 minutes andat a main shaft rotation speed of 75/min. The melt blending in theBrabender kneader was done under a nitrogen atmosphere.

TABLE 1 Ligth stabilizer compositions Sample No. HALS FRI concentration[pph] MB 1 15% C-944 0 MB 2 15% C-944 0.1 MB 3 15% C-944 0.5 MB 4 15%C-944 1.5 MB 5 15% T-770 0 MB 6 15% T-770 0.5 MB 7 15% PR-31 0 MB 8 15%PR-31 0.5 C-944 = Chimassorb ® 944, T-770 = Tinuvin ® 770, PR-31 =Sanduvor ® PR-31

The prepared compositions were used for light stabilization ofpolypropylene (MFI=0.7 g/10 min at 230° C. and 2.16 kg) The PP powderwas dry blended with 1% of ground composition (i.e. 0.15% concentrationof HALS in the final stabilized PP polymer) and with 0 1% calciumstearate and 0.05% phenolic antioxidant (Irganox 1010).

These compositions were then melt homogenized by two extrusions in asingle screw laboratory extruder at 210° C. and 270° C., respectively.The obtained stabilized polypropylene pellets were pressed at 230° C. togive 0.1 mm polymer films that were exposed to accelerated weatheringtest according to ASTM D-5208. The light stability of the individualsamples was assessed according to development of carbonyl oxidationproducts in the exposed polymer films as measured by infraredspectroscopy.

The results of the carbonyl absorption measurements (Aco) after 1000hours exposition to accelerated weathering (UV-A) are given in Table 2.

TABLE 2 Carbonyl index values of UV-stabilized PP-samples Sample No.Light stabilization Aco after 1000 hours LS 1 1% MB 1 0.42 LS 2 1% MB 20.33 LS 3 1% MB 3 0.29 LS 4 1% MB 4 0.25 LS 5 1% MB 5 0.132 LS 6 1% MB 60.119 LS 7 1% MB 7 0.34 LS 8 1% MB 8 0.28

EXAMPLE 2

Substrate: Polypropylene, type Profax 6508 (producer Himont, USA), basestabilized with 0.0114% Irganox 1076.

Prior to addition to this polymer, a masterbatch consisting of 15weight-% of the commercially available HA(L)S-based stabilizer Sanduvor3944 in polypropylene (Profax 6508) has been prepared at 200° C. using akneader, type Brabender Plasticorder PLE 651 at 75 rpm under nitrogen.

Pre-extrusion of polypropylene with 1 weight-% of this masterbatch, 0.05weight-% Irganox 1010, 0.10 weight-% Ca stearate and individually dosedamounts of the peroxide DBHP=Trigonox 101 is performed in a lab-extrudertype T4 Händle KPS 25 at T=210° C./80 rpm whereas the final extrusion iscarried out in an extruder, type T3 Göttfert at 270° C./50 rpm with adie diameter of 2 mm.

PP granules produced by means of this procedure have been used toprepare films of the dimension 140×140×0.1 mm using a lab press, typeFontjneTP 600, at a temperature of T=230° C. and a pressure of 120 kNduring 90 seconds. These films are submitted to artificial weatheringtests by means of both Uvicon (UV-A) and Weather-o-meter CAM-7. The UV-Atest is realized according to ASTM G 53 at a wavelength λ_(max)=340 nmwith exposure intervals of 20 hours followed by a dark period of 4hours. Measuring parameter is the time/hours to reach a carbonylabsorption of 0.5. The CAM-7 experiment is conducted according to DIN 53385A using an UV-lamp with a power output of 6500 Watt. Dry periods of102 minutes are followed by wet periods of 18 minutes. Measuringparameter is the time/hours to reach a carbonyl absorption of 0.3.Resulting data are summarized in table 1.

TABLE 1 UV-A, time to CAM-7, time to delta C═O = 0.5/ delta C═O = 0.3/Formulation hours hours BS + 0.15% Sanduvor 3944 1208 1682 w/o Trigonox101 BS + 0.15% Sanduvor 3944 + 1264 1783 0.1% Trigonox 101 BS + 0.15%Sanduvor 3944 + 1361 1827 0.5% Trigonox 101 BS + 0.15% Sanduvor 3944 +1486 1914 1.5% Trigonox 101 BS (base stabilization): 0.05% Irganox1010 + 0.10% CaSt

What is claimed is:
 1. A light stabilizer composition made by theprocess comprising the steps of: a) mixing a polymer with at least onepolyalkylpiperdine wherein the polyalkylpiperidine is present in anamount from 0.1 to 70% by weight, based on the weight of thecomposition, and wherein the polyalkylpiperidine is an oligomeric or ahigh molecular-weight polyalkylpiperidine selected from the groupconsisting of compounds of formulae (I) to (VIII)

 poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetra-methylpiperidyl)-amino]-hexamethylene-[4-(2,2,6,6-tetramethylpiperidyl)-imino]}(I),

 1,3,5-triazine-2,4,6-triamineN,N′″-[1,2-ethane-diyl-bis[[[4,6-bis-[butyl(1,2,2,6,6-penta-methyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl]imino]-3,1-propanediyl]]bis[N′,N″-dibutylN′,N″-bis(1,2,2,6,6,-pentamethyl-4-piperidinyl)-(II),

 poly-[(6-morpholino-s-triazine-2,4-diyl)-[2,2,6,6-tetramethyl-4-piperidyl)imino]-hexa-methylene[(2,2,6,6-tetramethyl-4-piperidyl)imino](III),

 poly-(N-β-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidyl-succinate)(IV),

 polymethylpropyl-3-oxy-[4(2,2,6,6-tetramethyl)-piperidinyl]-siloxane(V), Oligomer obtained by the reaction and subsequent oligomerization of2,2,4,4-tetramethyl-21-oxo-7-oxa-3,20-diazadispiro-[5.1.11.2]-heneicosaneor its hydrochloride with epichlorohydrine, (VI),

 1,3-propanediamine, N,N″-1,3-ethanediylbis-, polymer withN-butyl-2,2,6,6-tetramethyl-4-piperidinamine and2,4,6-trichloro-1,3,5-triazine (VII),

 poly-[3-elcosyl-(-tetracosyl)-1-(2,2,6,6-tetramethylpiperidin-4-yl)-pyrrolidin-2,5-dione](VIII), or a low molecular-weight polyalkylpiperidine selected from thegroup consisting of compounds of formulae (IX) to (XIII):

 bis-2,2,6,6-tetramethyl-4-piperidyl-sebacate (IX),

 propanedioicacid,[(4-methoxyphenyl)-methylene]-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)ester(X),

 a mixture of esters of 2,2,6,6-tetramethyl-4-piperidinol and higherfatty acids (mainly stearic acid) (XI),

 2,2,6,6-tetramethyl-21-oxo-7-oxa-3,20-diazadispiro[5.1.11.2]-heneicosane(XII),

 2,2,4,4-tetramethyl-21-oxo-7-oxa-3,20-diazadispiro[5.1.11.2]-heneicosan-20-propanoic-acid-dodecylester(XIII), or a polymer bound polyalkylpiperidine, and at least one freeradical generator to form a mixture b) melt-blending of the mixture at atemperature above the melting point of the polymer and above thedecomposition temperature of the free radical generator and at shearconditions sufficient to blend the components.
 2. A light stabilizercomposition according to claim 1 wherein the free radical generator is aperoxide or hydroperoxide compound.
 3. A light stabilizer compositionaccording to claim 1 wherein the free radical generator is selected fromthe group consisting of dicumylperoxide;2,5-bis-tert.-butyl-peroxy-2,5-dimethylhexane; di-tert.-butylperoxide;isopropyl-tert.-butyl peroxy carbonate;bis(tert.-butyl-2-peroxyisopropyl)-1,3-benzene;dimethyl-2,5-bis-(tert.-butyl-peroxy)-2,5-hexane;2,5-dimethyl-2,5-bis-(tert.-butylperoxy)-hex-3-yne;tert.-butyl-cumylperoxide; and bis-(tert.-butyl)-3,3-ethyl-butyrate. 4.A light stabilizer composition according to claim 1, wherein the amountof the free radical generator is from 0.01 to 10% by weight, based onthe weight of the polymeric composition.
 5. A light stabilizercomposition according to claim 1, wherein the polymer is a thermoplasticorganic polymer.
 6. A light stabilizer composition according to claim 1,wherein the polymeric composition further comprises at least oneadditive.
 7. A method for enhancing the light stability of a polymercompound comprising incorporating into the polymer compound, before orduring processing, a stabilizing quantity of the stabilizer compositionmade according to claim
 1. 8. A light stabilizer composition accordingto claim 1, wherein the free radical generator is an organic peroxidecompound.
 9. A light stabilizer composition according to claim 1,wherein the amount of the polyalkylpiperidines is from 5 to 30% byweight, based on the weight of the polymeric composition.
 10. A lightstabilizer composition according to claim 1, wherein the amount of thefree radical generator is from 0.1 to 2% by weight, based on the weightof the polymeric composition.
 11. A light stabilizer compositionaccording to claim 5, wherein the thermoplastic organic polymer isselected from the group consisting of polyolefins, copolymers and blendsthereof.
 12. A light stabilizer composition according to claim 6,wherein the at least one additive is selected from the group consistingof antioxidants, UV-absorbers, pigments, dyes, nucleating agents,fillers, and property modifiers.
 13. A polymer compound made inaccordance with the method of claim
 7. 14. A polymer compound comprisingthe light stabilizer composition made in accordance with the process ofclaim 1.